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Abstract Under warming conditions and with increasing human perturbations, rivers across the globe are facing drastic shifts in their hydrologic regime, resulting in fragmentation and disconnection from the catchment. Subsequently, a dependency on in situ primary productivity as the source of organic matter increases and warrants detailed investigation of the nature of primary production in urbanized river systems. In this study, primary productivity was estimated at multiple locations along the continuum of an engineered (Sabarmati) and a free flowing (Mahi) river systems in India using 13C tracer incubation method. Significantly enhanced primary productivity in the riverfront (engineered construction along the Sabarmati that holds water supplied by a canal) and polluted downstream of the Sabarmati compared to free flowing Mahi was observed. It was also observed that water stagnancy, temperature, and nutrient availability were the key factors regulating the rates of primary productivity in the urban river system. The study highlights the salient features of riverine primary productivity associated with engineered modifications, which needs to be considered for future river development projects.

Source‐to‐sink transfer of sediment and organic carbon (OC) is regulated by river mobility. Quantifying trends in river mobility is, however, challenging due to diverse planform morphologies (e.g., meandering, braided) and measurement methods. Here, we utilize a remote‐sensing method applicable to all planform morphologies to quantify the mobility timescales of 80 rivers worldwide. Results show that, across the continuum from meandering to braided rivers, there is a systematic reduction in the timescales of channel mobility and—to a lesser extent—floodplain reworking. This leads to a decrease in the efficiency with which braided rivers rework old floodplain material compared to their meandering counterparts. Reduced floodplain reworking efficiency of braided rivers leads to smaller channel‐belt areas relative to their size. Results suggest that river‐mobility timescales derived from remote sensing can aid in the characterization of sediment and OC storage and transit times at a global scale. Plain Language Summary: Rivers transport sediment and organic carbon (OC) from the mountains to the sea, and river movement affects sediment and OC transit times in landscapes. Understanding the controls on timescales of river movement is critical for assessing how fluvial processes influence the terrestrial carbon cycle. While previous work has quantified different river planform shapes on the Earth's surface (e.g., meandering, wandering, and braided), little is known about how the pace and nature of river movement is different between river planform shapes. This is because we lack methods to measure and compare river movement across different river planform shapes. Here, we leverage a tool to quantify river movement from time series of satellite imagery that is equally applicable to all river planform shapes. We apply this method to calculate the timescales of river movement of 80 rivers worldwide for the last 37 years. We show that (a) braided rivers migrate faster than meandering rivers, and (b) braided rivers move over a smaller area relative to their size. Comparing results with geochemical observations from the Río Bermejo—a well‐studied river for sediment‐OC cycling—we show that our mobility framework may provide a new way to assess sediment and OC storage timescales in floodplains. Key Points: We quantify timescales of floodplain reworking and channel‐overlap decay from satellite imagery of 80 rivers worldwideFrom meandering to braided planform morphology, there is a reduction in the overlap timescale and the reworking timescaleMobility timescales provide a means for remotely quantifying terrestrial‐sediment and organic‐carbon storage and transit [ABSTRACT FROM AUTHOR]

We consider unconfined flow in aquifers with a small sloping base, a magnitude of no more than a few percent at maximum and aim the analysis to large-scale regional modeling using analytic elements. We write the equations for the vertically integrated discharge, and find that the resulting two-dimensional discharge vector is rotational, as opposed to the specific discharge vector. We propose an approximate model for describing three-dimensional flow in an aquifer with a sloping base, and apply the approach to cases of flow between two parallel rivers and flow with a well in an aquifer bounded by a long river. We apply Wirtinger calculus and are able to estimate the error due to the approximation. [ABSTRACT FROM AUTHOR]

Stream connectivity restoration through the removal or mitigation of dams and other anthropogenic barriers is critical for aquatic species conservation. Historically, stream connectivity restoration planning has been focused on biophysical criteria; however, aquatic barriers are embedded in social contexts that can constrain restoration decisions. To support the integration of social considerations into stream connectivity conservation planning, we synthesized the available research involving social criteria linked to barrier removal. We found that the literature has been focused predominantly on the removal of dams and identify four major categories of social considerations for barrier removal: economics, nonmarket social values, safety, and procedural context. We reviewed contemporary barrier removal prioritization efforts and found that existing approaches typically only consider small subsets of social considerations and face issues with data availability. The findings synthesized in the present article establish potential criteria that could be integrated into effective stream connectivity restoration planning and inform future data capture efforts for barrier removal. [ABSTRACT FROM AUTHOR]

In the article the author shares the important role of the Schuylkill River located in Pennsylvania in writing her book "Utopia Found and Lost in Penn's Woods." Topics include brief description of the ecological location of the river, emphasis by scholars on the humanistic objects of inquiry and the concept of Black ecologies by authors J. T. Roane and Justin Hosbey.

The Caucasus is characterized by the large and at the same time increasing load from exploited metal and non-metallic mines. The sanitary-hygienic and toxic danger to people and the environment is quite high. There are 44 metal ores in the Syunik Region, and more than 90 non-metal deposits. In 2018, 12 metal and 29 non-metallic deposits were granted with the use rights for the purpose of mineral extraction. Also, geological survey permission was granted for 12 metal deposits. Currently, there are 12 operating and conserved tailings filled with about 400 million m3 of tailings, which are equipped with many heavy metals and other dangerous substances, as the result of the exploitation of the metal mines in Syunik. The present study focuses on the ecological assessment of the waters of the Voghji and the Khalaj Rivers that are located in the technogenic polluted zone of the Caucasus. The research revealed that along with the increase of the volumes of the Kapan-Qajaran copper-molybdenum mines, as well as the increase of the rock dumps and tailings, the organoleptic-chemical indicators of the waters of the Voghji and the Khalaj Rivers had increased. The quantity of the suspended particles and the heavy metals in the waters of these rivers had increased 1.5 and 2.0 times or by 58–100 % and 19.5 − 29.8 %, respectively, in the last 10 years. The trends are also observed in the values of the sulfates, the total dissolved salts, and the electrical conductivity, which are due to the chemical composition of the ores and the improper management of the acid drainage. The content of the heavy metals in the waters of the mentioned rivers is 9 − 20 times higher than the permissible limit density, and the degree of the mineralization is above the permissible limit. Thus, the waters of these rivers, after mixing with the effluent from the mining industry, are not guaranteed to be used for irrigation. Considering that the mobility of the heavy metals decreases several times in the alkaline environment (pH 8.5 − 9.0), it is recommended that the mining industry constantly adds lime (CaO) to the acid drainage of the mines so that the pH of the water become lower: from acid to alkaline (pH 8.5 − 9.0) and only after that, the water could be used for irrigation of the agricultural crops. This is possible for many types of heavy metals, including when using other wastewater treatment measures: engineering, physicochemical and biological. [ABSTRACT FROM AUTHOR]

Cutting-edge technology for fluvial monitoring has revolutionised the field, enabling more comprehensive data collection, analysis, and interpretation. Traditional monitoring methods were limited in their spatial and temporal resolutions, but advancements in remote sensing, unmanned aerial systems (UASs), and other innovative technologies have significantly enhanced the fluvial monitoring capabilities. UASs equipped with advanced sensors enable detailed and precise fluvial monitoring by capturing high-resolution topographic data, generate accurate digital elevation models, and provide imagery of river channels, banks, and riparian zones. These data enable the identification of erosion and deposition patterns, the quantification of sediment transport, the evaluation of habitat quality, and the monitoring of river flows. The latter allows us to understand the dynamics of rivers during various hydrological events, including floods, droughts, and seasonal variations. This manuscript aims to provide an update on the main research themes and topics in the literature on the use of UASs for river monitoring. The latter is achieved through a bibliometric analysis of the publication trends and identifies the field's key themes and collaborative networks. The bibliometric analysis shows trends in the number of publications, number of citations, top contributing countries, top publishing journals, top contributing institutions, and top authors. A total of 1085 publications on UAS monitoring in rivers are identified, published between 1999 and 2023, showing a steady annual growth rate of 24.44%. Bibliographic records are exported from the Web of Science (WoS) database using a comprehensive set of keywords. The bibliometric analysis of the raw data obtained from the WoS database is performed using the R software. The results highlight important trends and valuable insights related to the use of UASs in river monitoring, particularly in the last decade. The most frequently used author keywords outline the core themes of UASs monitoring research and highlight the interdisciplinary nature and collaborative efforts within the field. "River", "topography", "photogrammetry", and "Structure-from-Motion" are the core themes of UASs monitoring research. These findings can guide future research and promote new interdisciplinary collaborations. [ABSTRACT FROM AUTHOR]

The present work concerns the interaction between hydraulic processes and biological communities in rivers. In particular, the aim of this study is to investigate the interactions between flow dynamics and the freshwater mussels (FMs) to verify if the mussels' behavioural response to the hydrodynamic stress could be used to monitor natural extreme events in rivers. Although the influence of mussels on the kinematic characteristics of flow at the water–sediment interface was investigated by a certain number of studies, their behavioural response to flow, both in static and dynamic conditions, remains understudied. Laboratory experiments were performed in an artificial flume exposing Unio elongatulus to different values of flow discharge, both in steady and in unsteady conditions either with or without sediment transport. Mussels' behavioural responses were detected by using Hall sensor technology to measure gaping frequency, amplitude and duration, both in static conditions and under the effect of hydrodynamic stresses. Five categories of behavioural response were identified: Normal Activity (NA), Resting (Re), Transition (Tr), Adaptation (Ad) and Avoidance (Av). During NA (standard feeding and moving), FMs presented valve gaping, while during Re valves were kept constantly opened for water filtration. After a variation of flow discharge (ΔQ), FMs promptly reacted showing a transition from their normal behaviour, with constant gaping frequency (below 0.01 Hz), to higher valve gaping frequencies. The mean valves' gaping frequency increased as a function of ΔQ, and the highest values were reached in the presence of sediment transport. The mean valve opening amplitude was less sensitive to ΔQ. Its range of variation was very narrow with the highest values corresponding to the protrusion/retraction of the animals' foot to move or anchor to the substrate. The percentage of mussels responding to the discharge variation (Transition behaviour) increases with ΔQ confirming that mussels' behavioural response represents a promising tool for monitoring the occurrence of hydrodynamic stressors in fluvial systems. [ABSTRACT FROM AUTHOR]

Habitat fragmentation is emerging as a leading cause of biodiversity decline in riverine ecosystems. Several natural and human factors contribute to the fragmentation of rivers. River fragmentation is a growing problem that is widely spread and poses a significant challenge to the conservation of freshwater biodiversity, but its impact is not fully documented and acknowledged. Fragmentation impedes the movement of aquatic organisms and alters natural flow regimes, disrupting habitats and trophic supplies for aquatic biodiversity. It can also affect the adaptive ability of organisms to natural environmental changes, leading to a change in the structure and function of biotic communities. To understand the effects of fragmentation on river ecology, it is crucial to link its spatial and structural implications. This article examines the occurrence and frequency of fragmentation and its effects on the ecological community of benthic biota. This review aims to elucidate the overall effects of fragmentation on river ecology and recommends the possible measures to mitigate its impact. Urgent action is required to establish a comprehensive global network of free‐flowing river systems and revive previously exploited rivers in different regions to enhance the protection and sustainable utilization of river ecosystems. [ABSTRACT FROM AUTHOR]

Sediment ratings supply an important input to the design of water resources projects. Nevertheless, the accuracy of sediment ratings has remained a matter of concern for hydrologists. The present article investigates both the aspect of improving the accuracy, i.e., modifying the simple rating curve equation by introducing a four-parameter equation and application of ensemble machine learning (ML) and ensemble empirical models, to estimate sediment loads. The ML models include artificial neural networks, multi-gene genetic programming (MGGP), and a hybrid MGGP-based model. Published field data at two measuring stations were used to assess the performance of different models employed in this study. The comparative analysis conducted in this study provides a novel comparison of sediment load estimations for three time scales. For instance, the ML-based simple average ensemble model (i.e., 556.5, 255.0, and 0.759) and the empirical-based nonlinear ensemble model (i.e., 549.1, 378.6, and 0.589) achieved the lowest root-mean-square errors and mean absolute errors and highest determination coefficients for the train and test monthly sediment data of the first station, respectively. Finally, the findings demonstrate that ensemble-based models generally improve the estimates of sediment loads at daily, 10-daily, and monthly scales. [ABSTRACT FROM AUTHOR]

Rivers provide key ecosystem services that are inherently engineered and optimized to meet the strategic and economic needs of countries around the world. However, limited water quality records of a full river continuum hindered the understanding of how river systems response to the multiple stressors acting on them. This study highlights the use of Sentinel-2 Multi-Spectral Imager (MSI) data to monitor changes in water color in two optically complex river systems: the Yangtze and Danube using the Forel-Ule Index (FUI). FUI divides water color into 21 classes from dark blue to yellowish brown stemming from the historical Forel-Ule water color scale and has been promoted as a useful indicator showing water turbidity variations in water bodies. The results revealed contrasting water color patterns in the two rivers on both spatial and seasonal scales. Spatially, the FUI of the Yangtze River gradually increased from the upper reaches to the lower reaches, while the FUI of the Danube River declined in the lower reaches, which is possibly due to the sediment sink effect of the Iron Gate Dams. The regional FUI peaks and valleys observed in the two river systems have also been shown to be related to the dams and hydropower stations along them. Seasonally, the variations of FUI in both systems can be attributed to climate seasonality, especially precipitation in the basin and the water level. Moreover, land cover within the river basin was possibly a significant determinant of water color, as higher levels of vegetation in the Danube basin were associated with lower FUI values, whereas higher FUI values and lower levels of vegetation were observed in the Yangtze system. This study furthers our knowledge of using Sentinel-2 MSI to monitor and understand the spatial-temporal variations of river systems and highlights the capabilities of the FUI in an optically complex environment. [ABSTRACT FROM AUTHOR]

The water crisis may be solved by utilizing reclaimed water. Three reclaimed water sources have restored the lower sections of the Licun River, forming a landscaped river. In this paper, the river's water quality was monitored for a year, and the ecological concerns were analyzed using luminescent bacteria, chlorella, and zebrafish. The results indicated that although basic water quality indicators like COD and ammonia fluctuated along the river, the classification of water quality was primarily affected by factors such as flow rate and water depth. Under experimental conditions, the toxic inhibitory effect of river water on luminescent bacteria, chlorella, and zebrafish was related to the treatment process of reclaimed water. It was found that the reclaimed water produced by the MBR, along with the UV disinfection process, showed no detectable toxicity. In contrast, the MBBR process, when combined with coagulation, sedimentation, filtration, ozonation, and chlorination, seemed to be the source of this toxicity. Along the river, the results of water quality assessments and ecological risk assessments were different, indicating that both should be conducted to evaluate rivers replenished with reclaimed water. [ABSTRACT FROM AUTHOR]

To address ongoing threats from human pressures and climate changes, water managers and users require a visual tool that provides accurate information about the health of waterbodies for decision making. However, there is a lack of less sophisticated methods, such as biotic scoring, to assess the health of rivers in West Africa. To bridge this gap, we have developed a macroinvertebrate-based scoring system for monitoring the health of rivers in the Sahelian regions. We adopted a multi-habitat sampling approach to collect macroinvertebrates using hand nets, and these specimens were identified mostly to family taxonomic level using keys. We recorded more than 75 taxa of macroinvertebrates, each assigned relative sensitivity scores to human disturbances ranging from 1 (very tolerant) to 10 (highly sensitive). The Burkina Biotic Score System (BBIOSS) and the Average Score Per Taxa (ASPT) demonstrated a strong and significant correlation with environmental variables, including anthropogenic pressures types (r = 0.6; p < 0.01) making it a robust tool for monitoring rivers. Here, our findings revealed that all taxa scored are expected to be those reported in Western African freshwater. This study has produced an effective tool that can be used or adapted to monitor other riverine ecosystems in West Africa, potentially contributing to the preservation of water and biological resources. [ABSTRACT FROM AUTHOR]

When the Ebola virus crossed undetected into Sierra Leone and exacerbated the 2014-15 crisis, the World Health Organization blamed the breach on a traditional healer treating patients from Guinea. Meanwhile, local residents initially maintained that her death was not Ebola-related but a serpent's curse, an assumption grounded in lived experience of snake charmer spectacles. Both narratives drowned out evidence that the virus spread not via the healer's covert herbalism, but via her professional connections at the local government clinic and, more broadly, an overtaxed and undertrained public health system. This article takes local rumours around Ebola as vernacular epidemiologies that resonated with sensory experience. They show that both community and humanitarian actors had information; complications arose from the diverse experiences and expectations that shaped responses to that information. Such expectations emerge from the borderland geography, where colonial infrastructures continue to channel perception according to "upriver", "downriver", and "crossriver" phenomenologies. [ABSTRACT FROM AUTHOR]

In coastal regions, compound flooding, driven by multiple flood hazard sources, can cause greater damage than when the flood drivers occur in isolation. This study focuses on compound flooding from extreme precipitation and storm surge in China's Qiantang Estuary. We quantify the potential of compound flooding by measuring bivariate joint statistical dependence and joint return period (JRP). We find a significant positive dependence between the two flood drivers considered, as indicated by Kendall's rank correlation coefficients. Compound events occur frequently, with an average of 2.65 events per year from 1979 to 2018, highlighting the significant concern of compound flooding for this estuary. Using a copula model, we demonstrate that considering the dependence between the two flood drivers shortens the JRP of compound flooding compared to the JRP assuming total independence. For a 1-in-10-yr precipitation event and 1-in-10-yr storm surge event, the JRP is 1 in 100 years when assuming total independence. However, it decreases to 1 in 32.44 years when considering their dependence. Ignoring the dependence between flood drivers can lead to an increase in the JRP of compound events, resulting in an underestimation of the overall flood risk. Our analysis reveals a strong link between the weather patterns creating compound events and extreme storm surge only events with tropical cyclone activity. Additionally, the extreme precipitation only events were found to be connected with the frontal system of the East Asian summer monsoon. This study highlights the importance of considering the dependence between multiple flood drivers associated with certain types of the same weather systems when assessing the flood risk in coastal regions. [ABSTRACT FROM AUTHOR]

Microbial pollution of recreational waters leads to millions of skin, respiratory, and gastrointestinal illnesses globally. Fecal indicator bacteria (FIB) are monitored to assess recreational waters but may not reflect the presence of Staphylococcus aureus, a global leader in bacterial fatalities. Since many community‐acquired S. aureus skin infections are associated with high recreational water usage, this study measured and modeled S. aureus, methicillin‐resistant S. aureus (MRSA), and FIB (Enterococcus spp., Clostridium perfringens) concentrations in seawater and sand at six beaches in Hilo, Hawai'i, USA, over 37 sample dates from July 2016 to February 2019 using culturing techniques. Generalized linear models predicted bacterial concentrations with physicochemical and environmental data. Beach visitors were also surveyed on their preferred activities. S. aureus and FIB concentrations were roughly 6–78 times higher at beaches with freshwater discharge than at those without. Seawater concentrations of Enterococcus spp. were positively associated with MRSA but not S. aureus. Elevated S. aureus was associated with lower tidal heights, higher freshwater discharge, onsite sewage disposal system density, and turbidity. Regular monitoring of beaches with freshwater input, utilizing real‐time water quality measurements with robust modeling techniques, and raising awareness among recreational water users may mitigate exposure to S. aureus, MRSA, and FIB. Practitioner Points: Staphylococcus aureus and fecal bacteria concentrations were higher in seawater and sand at beaches with freshwater discharge.In seawater, Enterococcus spp. positively correlated with MRSA, but not S. aureus.Freshwater discharge, OSDS density, water turbidity, and tides significantly predicted bacterial concentrations in seawater and sand.Predictive bacterial models based upon physicochemical and environmental data developed in this study are readily available for user‐friendly application. [ABSTRACT FROM AUTHOR]

The objective was to evaluate the feasibility of measuring bathymetry using airborne green LiDAR in long and variable river reaches (4 km or more), across three rivers with varying gradients, water depths and light penetration (3.5–10 m), using four alternative LiDAR sensors. The accuracy of green LiDAR data was compared to in situ measurements collected by stratified transect point sampling and Multibeam bathymetry. Factors potentially limiting the feasibility of green LIDAR in rivers were explored. If remote sensing signals were reflected by the riverbed, the sensors generally provided elevation data consistent with in situ elevation measurements, indicating high accuracy (±10 cm) across different hydraulic conditions. The loss of green LiDAR data was mainly a consequence of limited signal water penetration capability, that is, water clarity. Secchi depth was a proxy variable strongly associated with green LiDAR penetration capability across rivers. Data loss was low up to the Secchi depth but increased rapidly thereafter. Surface water turbulence ('white water') and dark riverbed vegetation also increased green LiDAR signal loss. Sensors with lower point density and therefore less spatial resolution had more signal strength and therefore penetrated deeper water. However, with increasing coverage of surface turbulence ('white water'), the importance of high point density also increased. Signal power should be balanced with signal density (spatial resolution), depending on river characteristics and project objectives. We conclude that remote sensing green LiDAR bathymetry is a robust method that efficiently provides accurate elevation data across rivers with different hydraulic conditions and water depths. [ABSTRACT FROM AUTHOR]

The objective of the current research was to examine the water quality of the River Ravi and the River Sutlej, with a specific focus on potentially toxic elements (PTEs). Additionally, we sought to monitor the sources of pollution in these rivers by gathering samples from the primary drains that carry industrial and municipal waste into these water bodies. Furthermore, we aimed to evaluate the impact of PTEs in surface water on groundwater quality by collecting groundwater samples from nearby populated areas. A total of 30 samples were collected from these three sources: rivers (6 samples), drains (9 samples), and groundwater (15 samples). The analysis revealed that the levels of PTEs in the samples from these three resources having a mean value: arsenic (As) 23.5 µg/L, zinc (Zn) 2.35 mg/L, manganese (Mn) 0.51 mg/L, lead (Pb) 6.63 µg/L, and chromium (Cr) 10.9 µg/L, exceeded the recommended values set by the World Health Organization (WHO). Furthermore, PTEs including (As 84%), (Zn 65%), (Mn 69%), (Pb 53%), (Cr 53%), and (Ni 27%), samples were beyond the recommended values of WHO. The results of the Principal Component Analysis indicated that surface water and groundwater exhibited total variability of 83.87% and 85.97%, respectively. This indicates that the aquifers in the study area have been contaminated due to both natural geogenic factors and anthropogenic sources. These sources include the discharge of industrial effluents, wastewater from municipal sources, mining activities, agricultural practices, weathering of rocks, and interactions between rocks and water. Spatial distribution maps clearly illustrated the widespread mobilization of PTEs throughout the study area. Furthermore, a health risk assessment was conducted to evaluate the potential adverse health effects of PTEs through the ingestion of drinking groundwater by both children and adults. Health risk assessment result show the mean carcinogenic values for As, Cr, Pb and Ni in children are calculated to be (1.88E-04), (2.61E-04), (2.16E-02), and (5.74E-05), respectively. Similarly, the mean carcinogenic values for the above mentioned PTEs in adults were recorded to be (2.39E-05), (3.32E-05), (1.19E-03), and (7.29E-06) respectively. The total hazard index values for As, Zn, Cr, Pb, Mn, Cu, and Ni in children were observed to be (9.07E + 00), (9.95E-07), (4.59E-04), (5.75E-04), (4.72E-05), (2.78E-03), and (5.27E-05) respectively. The analysis revealed that As has an adverse effect on the population of the study area as compared to other PTEs investigated in this study. [ABSTRACT FROM AUTHOR]

India boasts of a vast freshwater resource network (rivers, wetlands, and groundwater), which has unique ecological, social and economic values associated with it. Despite their importance for both people and biodiversity, its freshwater ecosystems (FWEs) are heavily impacted through multiple factors such as pollution, overexploitation, habitat loss/modification and climate change. India is also among the hotspots of water resource overuse that has caused a serious decline in freshwater availability.Given that healthy FWEs lie at the centre for supporting the country's ecology, health, economy, livelihoods and ultimately achieving multiple policy goals, it is crucial that holistic and focused efforts are made to protect, conserve, and restore all types of FWEs.We call for an urgent and a greater focus on implementing conservation actions for FWEs in India and suggest the following strategy to enhance focus on their conservation: (1) establishing a shared freshwater conservation vision at a national scale, (2) developing and including national freshwater conservation goals within global efforts, (3) conducting simultaneous conservation action planning at regional scales and (4) bridge planning to implementation gap by strengthening key enabling conditions: i) mainstream FWE conservation within key existing governance instruments, ii) secure sustainable conservation funding, iii) improve data access and knowledge translation; iv) create national awareness around importance of FWEs; v) facilitate collaboration among key actors. [ABSTRACT FROM AUTHOR]

Introduction: Information on spatial patterns of water depth in river channels is valuable for numerous applications, but such data can be difficult to obtain via traditional field methods. Ongoing developments in remote sensing technology have enabled various image-based approaches for mapping river bathymetry; this study evaluated the potential to retrieve depth from multispectral images acquired by an uncrewed aircraft system (UAS). Methods: More specifically, we produced depth maps for a 4 km reach of a clearflowing, relatively shallow river using an established spectrally based algorithm, Optimal Band Ratio Analysis. To assess accuracy, we compared image-derived estimates to direct measurements of water depth. The field data were collected by wading and from a boat equipped with an echo sounder and used to survey cross sections and a longitudinal profile. We partitioned our study area along the Sacramento River, California, USA, into three distinct sub-reaches and acquired a separate image for each one. In addition to the typical, self-contained, per-image depth retrieval workflow, we also explored the possibility of exporting a relationship between depth and reflectance calibrated using data from one site to the other two sub-reaches. Moreover, we evaluated whether sampling configurations progressively more sparse than our full field survey could still provide sufficient calibration data for developing robust depth retrieval models. Results: Our results indicate that under favorable environmental conditions like those observed on the Sacramento River during low flow, accurate, precise depth maps can be derived from images acquired by UAS, not only within a sub-reach but also across multiple, adjacent sub-reaches of the same river. Discussion: Moreover, our findings imply that the level of effort invested in obtaining field data for calibration could be significantly reduced. In aggregate, this investigation suggests that UAS-based remote sensing could facilitate highly efficient, cost-effective, operational mapping of river bathymetry at the reach scale in clear-flowing streams. [ABSTRACT FROM AUTHOR]

Pollution of water bodies with heavy metals can lead to the death of fish and other aquatic organisms, a decrease in biodiversity and a threat to ecosystems, emphasising the importance of preserving the natural environment; pollution of water bodies can have serious economic consequences, in particular, a decrease in profits from fishing, tourism, and other activities related to water use, which requires the development of water management strategies. The purpose of the study was to determine the general trends in the content of heavy metals in the surface waters of the Teteriv River and fattening pond No. 1 of the LLC "SHF INTERRYBHOSP". Water samples were taken at the stream of the Teteriv River (Vidsichne Reservoir) and in the fattening pond No. 1 at a depth of 0.2-0.5 m from the surface for further laboratory analysis of the content of heavy metal ions (HM). The atomic absorption method of analysis was used to study water. Laboratory studies of surface waters in the Teteriv River and pond were performed according to the following indicators: hydrogen index (pH), lead, cadmium, manganese, zinc, and iron content. The results of the study of the content of heavy metals in the Teteriv River are presented, which showed that the content of such heavy metals as: Pb, Cd, Mn, Zn and Fe, in river water, with the exception of iron, exceed the limits of maximum admissible values of water quality indicators for fishery water bodies. Background HM indicators from fattening pond No. 1 did not show an excess of the MAC (maximum admissible concentration). High concentrations of lead, cadmium, manganese, and iron are explained by powerful anthropogenic pollution, the source of which is agricultural and industrial complexes of Zhytomyr Oblast. The results can be used to establish effective monitoring of water quality in reservoirs and develop strategies to reduce pollution in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Plastic pollution is now recognised as a growing concern for both the environment and associated biota. Consequently, a plethora of scientific reports are being produced regarding the occurrence, distribution, and transfer pathways of litter particles. However, there are scientific gaps that need to be filled regarding micro- and nanoplastic impacts on marine and freshwater organisms. This Special Issue (SI) aimed to provide an update on plastic pollution and its consequences on aquatic ecosystems, with a particular focus on biological domains, by adopting a multidisciplinary perspective. Several research articles and reviews were collected, focusing on the origin, fate, and effects of plastics in marine and freshwater environments, along with their interactions with biotic components. We believe this SI will contribute to the development of new studies on plastic pollution and the elaboration of science-based policies at different levels of our modern society. [ABSTRACT FROM AUTHOR]

This article discusses the governance aspects of managing river, lake, and aquifer basins, both at the transboundary and domestic levels. It highlights the importance of basin organizations in facilitating negotiation, data sharing, and decision-making among stakeholders. The article also explores the challenges faced by international basin organizations, such as power asymmetries and the inclusion of non-state actors. Additionally, it examines the scale implications of transboundary agreements and the participation of civil society in water management. The article concludes by emphasizing the need for improved institutions and cooperation in order to effectively manage water resources. [Extracted from the article]

This study aimed to optimize the methods for sampling and analyzing methylmercury (MeHg) concentrated within diffusive gradients in thin films (DGT) and its application to different water bodies. We explored the elution solution for MeHg, comprised of 1.13 mM thiourea and 0.1M HCl, optimizing its volume to 50 mL. In addition, we found that it is necessary to analyze the entire extraction solution after adjusting its pH, to ensure completion of the ethylation reaction. The DGT samplers were deployed in two distinct aquatic environments (i.e., Okjeong Lake and Nakdong River) for up to 6 weeks, and this study demonstrated to predict the time-weighted average concentration with a diffusion coefficient of 7.65 × 10−6 cm2 s−1 for MeHg in the diffusive gel. To assess the diffusive boundary layer (DBL) effects, the DGT samplers with different agarose diffusive gel thickness were deployed. The mass of MeHg accumulated in the DGT resin at a given time decreased with increasing diffusive gel thickness, because of creating longer diffusion pathways within thicker gels. The labile MeHg concentration estimated by the DGT in Okjeong Lake and Nakdong River are found in the range of 61–111 and 55–105 pg L−1, respectively, which were found to be similar to the grab sampling data. Additionally, this study evaluated depth-dependent MeHg in Okjeong Lake. The vertical profile results showed that the concentration of MeHg at the depth of 2.3 and 15.7 m are about 1.5 and 4.6 times of the DGT installed at 0.3 m of the surface layer, respectively, suggesting potential mercury methylation in deep waters. These findings have practical implications for predicting bioavailability, assessing risks, and formulating strategies for water body management and contamination remediation. [ABSTRACT FROM AUTHOR]

Iron (Fe) is one of the main nutrients present in dissolved, suspended, and colloidal states in river water. Predicting the composition and size of dissolved Fe compounds is crucial for assessing water quality. In this stud, we used a combination of physical methods (filtration), chemical techniques (ion exchange chromatography), and thermodynamic modeling (Visual MINTEQ) to characterize dissolved Fe speciation in boreal organic-rich rivers across a sizable south–north transect. We chose contrasting rivers with a predominance of either allochthonous or autochthonous organic compounds. We found that the dissolved organic matter (DOM) in the studied rivers varies in molecular weights and the degree of humification. Regardless of the climate parameters of the river watershed, the dominant status of dissolved Fe during the summer low-water period was essentially colloidal and dominated by anionic complexes of the type [MeL]n−. [ABSTRACT FROM AUTHOR]

There is an accumulation of toxic metal ions in an aquatic habitat that modifies the physical and chemical characteristics of water, posing a threat to aquatic organisms. The fish's body absorbs heavy metals through the gills, dorsal surface, and gastrointestinal system when they eat foodstuff that has high levels of these metals. Zinc, Lead, Mercury, Copper, Arsenic, Nickel, chromium and cadmium are the primary heavy metal contaminants responsible for inducing toxicity in fish. Oxidative stress, or oxidative damage, is the primary chemical process responsible for metal poisoning. Stress undermines a low immune system, leading to harm to organs and tissues, developmental irregularities, and reduced reproductive capacity. Due to the copious availability of vitamins, proteins, and fatty acids such as omega-3 found in fish, individuals are inclined to consume seafood as their primary nutritional source. Consequently, the aggregation of toxic metallic elements in fish tissues has a direct impact on people, causing detrimental effects that accelerate the onset of various diseases. To effectively enforce aquatic conservation regulations and protect human lives, it is imperative to investigate the origins of toxic metals and their detrimental effects on the health of fish. [ABSTRACT FROM AUTHOR]

The annual distribution characteristics of river runoff in arid regions have significant implications for water resource stability and management. Based on the mountain runoff data from 1965 to 2018, this study examines the annual change characteristics of monthly runoff of the Shiyang River Basin, Heihe River Basin, and Shule River Basin in the Hexi Corridor, Northwest China. Many indexes are used and analyzed, including the coefficient of variance, the complete regulation coefficient, the concentration degree and concentration period, the magnitude of change, the skewness coefficient, and the kurtosis coefficient of the annual distribution curves. The results reveal the following: (1) The inhomogeneity of annual runoff distribution in the Taolai River and the rivers to the west of it, except the Shiyou River, show an increasing trend. Conversely, the inhomogeneity of the rivers to the east of the Taolai River generally show a downward trend, but the coefficient of variance value is still very high. (2) In the Shiyang River Basin, the annual distribution of the concentration period is characterized by a relatively discrete pattern. Conversely, the Heihe River Basin exhibits a relatively concentrated pattern, and the distribution pattern of the Shule River Basin is quite different. Notably, all concentration periods in the three basins have shifted backward after the 2000s. (3) The Shiyang River Basin exhibits disordered annual distribution curves of runoff in different years. In contrast, the Heihe River Basin presents a typical ‘single-peak’ pattern with a prominent right-skewed. The Shule River Basin has regular distribution curves, with a gradually significant ‘double-peak’ pattern from east to west. Overall, there has been a slight change in runoff in the Shiyang River Basin, while the Heihe River Basin and Shule River Basin have experienced significant increases in runoff. The annual distribution curves of runoff in the Liyuan River and the rivers to the east of it exhibit a gentle peak pattern, and the appearance probability of extreme runoff during the year is low. Conversely, the rivers to the west of the Liyuan River, excluding the Danghe River, display a sharp peak and thick tail pattern, indicating that the appearance probability of extreme runoff during the year is high. These findings have practical implications for the planning and management of water resources in the Hexi Corridor. Moreover, they provide a solid foundation for predicting future changes in regional water resources. [ABSTRACT FROM AUTHOR]

This paper discusses water in Afghanistan from the late nineteenth century through the early twenty-first century. This broad chronology is periodized using the historical themes of colonialism, nationalism, international developmentalism, and global warfare. Modern hydraulic technology arrived in the domestic architecture of Kabuli state elites beginning in the 1860s and accelerating greatly in the 1890s. The first decades of the twentieth were marked by continuing developments regarding palatial hydrology (pools, fountains, etc.) and new forms of modern hydraulic engineering (piped water, dams and bridges) primarily in and around Kabul involving the Kabul river and its tributaries. The middle decades of the twentieth century involved substantial engagement of rivers throughout country under the various ideological and material regimes of international development sponsored by the US, USSR and a number of other global actors and sanctioned by local political elites who became increasingly dependent on the global system. The decades surrounding the year 2000 have been marked by intense and sustained overt and covert global warfare. The effects of war on the environment of Afghanistan from the perspective of Human Rights, particularly Afghan Peoples' Rights to Water, constitute the final section of the paper. [ABSTRACT FROM AUTHOR]

In the process of production or processing of materials by various methods, there is a need for a large volume of water of the required quality. Today in many regions of the world, there is an acute problem of providing industry with water of a required quality. Its solution is an urgent and difficult task. The water quality of surface water bodies is formed by a combination of a large number of both natural and anthropogenic factors, and is often significantly heterogeneous not only in the water area, but also in depth. As a rule, the water supply of large industrial enterprises is located along the river network. Mergers are the most important nodes of river systems. Understanding the mechanism of transport of pollutants at the confluence of rivers is critical for assessing water quality. In recent years, thanks to the data of satellite images, the interest of researchers in the phenomenon of mixing the waters of merging rivers has increased. The nature of the merger is influenced by the formation of transverse circulation. Within the framework of this work, a study of vorticity, as well as the width of the mixing zone, depending on the distance from the confluence, the speeds of the merging rivers and the angle of confluence was carried out. Since the consumer properties of water are largely determined by its chemical and physical indicators, the intensity of mixing, determined largely by the nature of the secondary circulation, is of fundamental importance for assessing the distribution of hydrochemical indicators of water quality in the mixing zone. These characteristics are important not only for organizing water intake for drinking and technical purposes with the best consumer properties, but also for organizing an effective monitoring system for confluence zones. [ABSTRACT FROM AUTHOR]

This paper presents a reassessment of mound visibility through the analysis of Halvdanshaugen, a substantial Iron Age mound in Norway. In line with conventional views, the mound's visibility covers a considerable swath of the surrounding terrain, although views are limited by topographic features from certain directions and specific parts of the landscape. A refined viewshed analysis, incorporating vegetation as a visual barrier, however, suggests that the mound's visual impact extends no more than a few hundred meters from its base. This sees the mound placed in an enclosed setting which alters the mound’s visual characteristics, emphasizing details of both the mound and activities nearby. In contrast to traditional interpretations that emphasize landscape-wide symbolism, this study advocates for a more reflective perspective, and calls for a multi-sensory understanding of the fluid relationship between mound and landscape. It rejects the idea of universal placement rules and proposes more contextual interpretations that acknowledge the diversity observed in mound construction and use.

The contribution of citizen scientists to environmental monitoring is notably increasing significantly. Governments worldwide establish Water Users Associations (WUAs) as a good practice model to implement Integrated Water Resource Management (IWRM) at local levels. These associations target different stakeholders depending on the expected outcome. However, their effectiveness, especially in East Africa, can only be determined case by case. In Kenya, Water Resources Users Associations are registered, voluntary community groups whose members are water users and land owners. Similarly, in Uganda, community-based initiatives exist, especially along degraded rivers, involving cooperation between local communities and regional water authorities. On the contrary, it has been reported that in Tanzania, many community initiatives created become non-functional within 2–3 years of induction. In general, the main responsibility of Water Users Associations or its equivalent is to manage and conserve water resources for sustainable uses. In most cases, water quality monitoring by communities through citizen science is limited to the visual appearance of water in the river channel. While this can indicate the water’s esthetic value, it is insufficient for assessing the ecological status of rivers, which is influenced by a variety of physical, chemical, biological, and socioeconomic factors. The use of bioindicators has been advocated as a feasible method for community-based water quality river monitoring. Therefore, this review explores the commonly used bio-indicators and bio-assessment tools for river health assessment and their complexities when using a biomonitoring community-based approach through citizen science. Tolerance and intolerance macroinvertebrate and fish metric protocols that utilize identification keys have been recommended. These protocols are designed to be user-friendly and require minimal taxonomic expertise, making them easy for community volunteers to use with minimal basic training. The sustainability of these citizen science initiatives relies on the motivation of volunteers, the frequency of monitoring activities, and collaboration with researchers and government agencies. These initiatives not only facilitate environmental monitoring but also foster community engagement and awareness regarding the ecological status of rivers, thereby addressing knowledge and data gaps necessary for effective policy-making. This approach provides a practical model for environmental stewardship and participatory resource management in East Africa.

In this study, we explored how barriers such as dams have affected the longitudinal connectivity of riverine habitats from the perspective of potamodromous fish. For this purpose, connectivity changes are investigated in the central part of the Austrian Danube system, where the national reporting for the EU Water Framework Directive provides detailed information on the position and characteristics of barriers as well as the distribution range of native fish species. This assessment is based on an estimation regarding the quantitative upstream and downstream passability of individual barriers, where we further investigate three different passability scenarios to account for uncertainties. We then apply several combinations of passability scenarios and assumptions on dispersal distances to calculate a series of network-based reach and catchment connectivity indices. On average, the estimation of barrier passability indicated a high downstream passability, while upstream passability was substantially lower across scenarios. Furthermore, existing fish passes were estimated to have increased passability on average between 20 % and 24 %. Overall, the results indicated a strong effect of barriers on the longitudinal connectivity of the investigated river network. Catchment scale indices revealed a loss of connectivity, which increased with dispersal distance. Reach connectivity indices displayed a strong disruption of the natural connectivity gradient along the river network and indicated that individual river reaches have, on average, become more isolated in addition to the overall decrease in connectivity. The average loss of connectivity across scenarios was estimated at 72 % (SD = 16 %) when taking into account all connections to other reaches and 66 % (SD = 7 %) when only connections to upstream reaches were considered. We conclude that longitudinal connectivity in the Austrian Danube system is still severely compromised, making it increasingly challenging for potamodromous fish species to complete their life cycle. This issue is further amplified by the severe loss of fish habitats as a consequence of river engineering.

This article explores how boat dwellers on the inland waterways of England and Wales – 'Boaters' – experience water and sanitation services. Boating populations are not counted as customers of private water utilities, so they exist within the 'dwelling paradox' and are positioned at greater risk of water and sanitation insecurity. Interviews and auto-ethnography document a myriad of ways in which participants use these resources on different vessels and waterways. The Capability Approach emerges as an apt framework for representing nuanced journeys from water and sanitation access to perceived quality of life. Findings suggest that equitable services can be defined as those which enable Boaters to live in ways they value. This entails reckoning with diverse – and potentially divergent – definitions of a 'good life', supported by the personal freedoms to achieve it. We argue this research makes a strong case for centring lived experiences in service design, particularly in instances of disagreement on the constitution of adequate service levels. Co-creating knowledge with people living in the dwelling paradox reveals complex relationships with authority and exclusion. We extend this theory, and the principles of equitable service delivery, to emphasise the situated desires, choices, and freedoms of the populations in question.

For the evaluation of the construction effect of engineering projects, this study combines the comprehensive evaluation index system and fuzzy mathematical methods, and improves the calculation process of the fuzzy matrix. A fuzzy mathematical method for the evaluation of river comprehensive improvement project is proposed. The results indicate that the comprehensive evaluation of river improvement benefits needs to start from four directions: engineering benefits, ecological benefits, economic benefits, and social benefits, with target layer weights of 0.2904, 0.4755, 0.0586, and 0.1755, respectively. The expert evaluation results indicate that most evaluation indicators of the project have a rating value greater than 5 points, and some indicators have a rating value of 8 points or above. This indicates that the evaluation samples for comprehensive river improvement in the research area perform well in most indicators and achieve good improvement results. The comprehensive evaluation index belongs to the second category of fuzzy values, and the effect of the river comprehensive improvement project is relatively ideal, which is consistent with the actual evaluation. The results indicate that this method converts qualitative indicators into quantitative indicators, making the evaluation results more comparable and quantifiable, which helps to promote the effective implementation of river regulation work.

Existing in situ global sediment monitoring limits our potential to answer regional and continental scale sediment transport questions. Remote sensing of rivers has an established history addressing these spatial and temporal data gaps but suffers from resolution and overpass timing tradeoffs. Satellite spatiotemporal data fusion can help alleviate these tradeoffs by “teaching” a coarse resolution sensor what it would have seen if it were a fine resolution satellite. In this study, we fuse Landsat/Sentinel-2 with MODIS to produce 30 m spatial data with Landsat bands and MODIS repeat frequency. We then create a database of 1.8M large river sediment concentrations derived from fused and nonfused images made over 1253 Continental United States sites, as validated with over 25 000 in situ measurements across these same sites. Combining fused and original images using a globally scalable workflow more than doubles training and prediction image data density with marginal loss in overall performance (combined model relative error 36% versus 33% landsat versus 39% fusion) and no loss in stability. Furthermore, we test our global model's ability to generate meaningful time series for individual large and small rivers included in and exogenous to the training data. Results indicate that global model skill holds when applied at a site, even out of sample, which paves the way for future sediment mapping in the MODIS era and shows the value of fusion for addressing hydrologic measurement challenges.

Freshwater salinisation and alkalinisation strongly depend on human and natural factors. We used an explainable machine learning approach to investigate the impact of natural and human factors on the salinity and alkalinity in rivers in the United States. The model achieved coefficient of determination of 0.89 for salinity predictions and 0.92 for alkalinity predictions. Shapley additive explanations revealed salinisation is driven mainly by human factors like population density (18 %) and impervious surface percentage (13 %) and natural factors like run-off (14 %). The alkalinisation is mainly influenced by natural processes such as runoff (36 %) and soil-pH (20 %).

Global industrialization has contributed substantial amounts of chemical pollutants in rivers, resulting in an uninhabitable state and impacting different life forms. Moreover, water macrophytes, such as water hyacinths, are abundantly present in polluted rivers, significantly affecting the overall water biogeochemistry. Bioremediation involves utilizing microbial metabolic machinery and is one of the most viable approaches for removing toxic pollutants. Conventional techniques generate limited information on the indigenous microbial population and their xenobiotic metabolism, failing the bioremediation process. Metagenomics can overcome these limitations by providing in-depth details of microbial taxa and functionality-related information required for successful biostimulation and augmentation. An in-depth summary of the findings related to pollutant metabolizing genes and enzymes in rivers still needs to be collated. The present study details bioremediation genes and enzymes functionally mined from polluted river ecosystems worldwide using a metagenomic approach. Several studies reported a wide variety of pollutant-degrading enzymes involved in the metabolism of dyes, plastics, persistent organic pollutants, and aromatic hydrocarbons. Additionally, few studies also noted a shift in the microbiome of the rivers upon exposure to contaminants, crucially affecting the ecological determinant processes. Furthermore, minimal studies have focused on the role of water-hyacinth–associated microbes in the bioremediation potentials, suggesting the need for the bioprospecting of these lesser-studied microbes. Overall, our study summarizes the prospects and utilities of the metagenomic approach and proposes the need to employ it for efficient bioremediation. [ABSTRACT FROM AUTHOR]

Incorporating societal considerations into decisions related to invasive species management is desirable, but can be challenging because it requires a solid understanding of the ecological functions and socio- cultural and economic benefits and values of the invaded environment before and after invasion. The ecosystem service (ES) concept was designed to facilitate such decision-making by establishing direct connections between ecosystem properties and human well-being, but its application in invasive species management has not been systematic. In this Discussion paper, we propose the adoption of the ES cascade model as a framework for understanding the environmental effects, costs and benefits associated with controlling an invasive shrub (Tamarix spp.) in riparian systems of the western United States. The cascade model has the advantage of explicitly dissecting social-ecological systems into five components: ecosystem structure and processes, ecological functions, ecosystem services, benefits and the economic and socio-cultural valuation of these services and benefits. The first two have received significant attention in the evaluation of Tamarix control effectiveness. The last three have long been implicitly acknowledged over decades of Tamarix management in the region, but have not been formally accounted for, which we believe would increase the effectiveness, accountability and transparency of management efforts. [ABSTRACT FROM AUTHOR]

Environmental influences on species' functional traits are important ecological issues to assess biodiversity. Relationships among fish abundance, their functional traits, and environmental conditions across different levels of anthropogenic impacts in a tropical Brazilian river were evaluated. We combined RLQ and fourth-corner methods, utilizing local environmental variables and the Human Footprint Index (HFI) as a human activities indicator. Three HFI levels (High, Intermediate, and Low) and short-term (1993–2009) impact changes at each location were assigned. Fish with internal fertilization and small body sizes were strongly associated with high HFI scores. Grass-dominated riparian areas were common in altered locations, whereas less altered localities exhibited the riparian cover dominated by trees. Highly altered areas showed high HFI, grass-covered riparian zones, and small-sized species with internal fertilization (e.g., Cyprinodontiformes like Poecilia vivipara, Poecilia reticulata, and Phalloceros caudimaculatus). In contrast, less altered areas had tree-lined riparian zones and medium to large-sized species with external fertilization and diverse traits. Underlying deterministic processes shape species distribution, tied to environment and traits. Filtering of traits in the most altered locations may favor small-sized species with internal fertilization. This approach, utilizing HFI and local variables to assess trait–environment relationships of riverine fish, facilitates understanding organisms' responses to environmental constraints. [ABSTRACT FROM AUTHOR]

The loose‐equilibrium concept (LEC) predicts that ecological assemblages change transiently but return towards an earlier or average structure. The LEC framework can help determine whether assemblages vary within expected ranges or are permanently altered following environmental change.Long‐lived, slow‐growing animals typically respond slowly to environmental change, and their assemblage dynamics may respond over decades, which transcends most ecological studies. Unionid mussels are valuable for studying dynamics of long‐lived animals because they can live >50 years and occur in dense, species‐rich assemblages (mussel beds). Mussel beds can persist for decades, but disturbance can affect species differently, resulting in variable trajectories according to differences in species composition within and among rivers.We used long‐term data sets (10–40 years) from seven rivers in the eastern United States to evaluate the magnitude, pace and directionality of mussel assemblage change within the context of the LEC.Site trajectories varied within and among streams and showed patterns consistent with either the LEC or directional change. In streams that conformed to the LEC, rank abundance of dominant species remained stable over time, but directional change in other streams was driven by changes in the rank abundance and composition of dominant species.Characteristics of mussel assemblage change varied widely, ranging from those conforming to the LEC to those showing strong directional change. Conservation approaches that attempt to maintain or create a desired assemblage condition should acknowledge this wide range of possible assemblage trajectories and that the environmental factors that influence those changes remain poorly understood. [ABSTRACT FROM AUTHOR]

Salinization is a global threat to freshwater habitats that has been intensified by climate change. Monitoring, assessment and management of salinity is therefore essential. The first step is to set criteria that are sufficiently stringent to protect ecosystem health. However, many countries have not yet defined criteria, and there are substantial differences between criteria. This has been noted in the EU, where salinity is a required “supporting element” for ecological status in inland waters but also for implementation of UN Sustainable Development Goal (SDG) indicator 6.3.2. for “good ambient water quality” where different approaches and widely different threshold values were reported for salinity criteria. Much of this information has not been published and is difficult to access, hindering further efforts to address the problem. We first discuss the implications of salinization for freshwater ecological health. We go on to discuss the principles and guidelines on how salinity criteria to protect ecology should be established. Next, we review salinity criteria submitted as part of implementation of SDG indicator 6.3.2 and the EU Water Framework Directive. Finally, we discuss setting salinity thresholds in an already-warming world and the challenges facing anyone trying to develop salinity criteria to protect freshwater ecosystems. This article is categorized under: Water and Life > Stresses and Pressures on Ecosystems Water and Life > Conservation, Management, and Awareness Science of Water > Water Quality [ABSTRACT FROM AUTHOR]

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Purpose: Anthropogenic land use change has caused an increase in particulate nutrient loads from catchments draining to the Great Barrier Reef (GBR). The research in GBR catchments has indicated that particulate nutrients are bioavailable to both freshwater and marine phytoplankton, but relative importance of this source of nutrients to the GBR is unknown. We quantified the contribution of this source of bioavailable nitrogen in a dry-tropics grazing and a wet-tropics fertilized mixed land use catchment of the GBR. Materials and methods: The different bioavailable nitrogen pools and associated processes through which dissolved inorganic nitrogen (DIN) is generated from eroded sediment (mass of DIN generated per mass of sediment) were identified. These pools and processes were quantified from a range of representative sediment sources (e.g. surface and subsurface soil and different land uses). We collected 17 sediment source samples in the wet tropics and 41 in the dry tropics. We combined the N pool concentration data with spatial and hydrological fine sediment modelling to estimate the contribution from different sources and processes/pools to the end-of-catchment DIN load. Results and discussion: The modelled load of DIN generated from sediment accounted for all the monitored DIN load in the grazing-dominated catchment but was insignificant in the fertilized mixed land use catchment. Sediment from surface erosion (hillslope erosion) and some soil types contributed disproportionally to the modelled DIN generation. Fast solubilisation of DIN was the main process in the catchments studied. The importance of mineralisation of the organic fraction increased with the time the sediment was in suspension. Conclusion: Particulate nutrients in sediment are a significant source of bioavailable nitrogen in eroding grazing catchments. The processes that drive this bioavailability are complex, vary with sediment source and operate at different timeframes and spatial scales. [ABSTRACT FROM AUTHOR]

The elevations of water surfaces hold important information on the earth's oceans and land surface waters. Ocean sea surface height is related to the internal change of the ocean's density and mass associated with ocean circulation and its response to climate change. The flow rates of rivers and volume changes of lakes are crucial to freshwater supplies and the hazards of floods and drought resulting from extreme weather and climate events. The Surface Water and Ocean Topography (SWOT) Mission is a new satellite using advanced radar technology to make headway in observing the variability of the elevation of water surfaces globally, providing fundamentally new information previously not available to the study of earth's waters. Here, we provide the first results of SWOT over oceans, rivers, and lakes. We demonstrate the potential of the mission to address science questions in oceanography and hydrology. Plain Language Summary: Earth is a water planet. The vast amount of ocean water has stored most of the heat released to the atmosphere since the Industrial Revolution through burning fossil fuels. Climate change is thus moderated by the ocean. Over land the freshwater in lakes, rivers, and reservoirs, a critical natural resource, is affected by the warming climate and direct human modifications. Processes of oceanic uptake of heat and carbon from the atmosphere and cycling of freshwater on land take place at spatial scales too small to have been adequately quantified from space. A new satellite, the Surface Water and Ocean Topography (SWOT) mission, was launched in December 2022. Using advanced radar technology, SWOT provides unprecedented global observations for understanding the ocean's role in climate change and how freshwater resources respond to human influence. SWOT observations near coasts will also advance understanding of how rising sea levels impact those coasts. Key Points: The first space observations of submesoscale ocean surface topography for understanding ocean's role in heat uptake from the atmosphereThe first space observations of the change of water storage of lakes and flow rates of rivers for understanding the freshwater cycleThe first space observations of the details of the change of coastal water levels to assess the impact of local sea level rise [ABSTRACT FROM AUTHOR]